As any man will tell you (especially in the weeks before Valentine's Day), gift-giving is a tricky business. Although men can use gifts to enhance their chances of getting laid, this can also leave them vulnerable to "gold-diggers" (a highly scientific term that describes women who use the promise of sex to get stuff from men, sometimes without actually putting out). So what kind of present can a guy give to improve his chances of getting laid while at the same time avoiding gold-diggers?

To answer this important question, the two (male) authors of the study "Costly but worthless gifts facilitate courtship" used a mathematical model to simulate various courtship conditions. Like real people, the simulated couple does not know for certain if their potential mate finds them attractive or not. The man offers the woman a gift, and the woman then decides whether or not to sleep with the man (a feminist study, this is not).

For the simulation, the mathematicians began by breaking a "typical" relationship into steps and then assigned probabilities to each decision based on how attractive each partner finds the other. First, the man decides which of three types of gift to offer the woman:

"A cheap gift [that] costs the male nothing and is worth nothing to the female; a valuable gift [that] costs the male X and carries a benefit X to the female if she accepts it; or an extravagant gift [that] also costs the male X, but is intrinsically worthless to the female."

Next, the female observes the gift, tries to determine if it is worthless to her or not, and decides whether to accept it. Then, based on the quality of the gift and the attractiveness of the male, the female decides whether or not to "mate" with the male (sorry, guys with great personalities - even if the female accepts the gift, she will not mate with an unattractive male). Finally, if they do hook up, the male also can decide whether or not to desert the female (a.k.a wham, bam, thank you ma'am).

The mathematicians worked through the various paths in this decision tree (see figure) and calculated the probability of each possible outcome given how attractive each partner finds the other and the values of the gifts. After many rounds of such simulation, the mathematicians determined which types of gifts resulted in the males getting the most sex without getting taken advantage of by gold-diggers:

"We find robust equilibrium solutions in which mating is predominantly facilitated by an ‘extravagant' gift which is costly to the male but intrinsically worthless to the female. By being costly to the male, the gift acts as a credible signal of his intentions or quality. At the same time, its lack of intrinsic value to the female serves to deter a ‘gold-digger', who has no intention of mating with the male, from accepting the gift. In this way, an economically inefficient gift enables mutually suitable partners to be matched."

So basically, if a guy wants to sleep with an attractive woman, but avoid getting taken advantage of by gold-diggers, he should offer an expensive gift that is worthless to the woman outside of her interactions with the guy. The authors suggest an "expensive outing" (perhaps a fancy vacation?) would be a good way to go. Are you listening, Kanye West?